(Received 17 November 2005; accepted 6 March 2006;
published online
17 June 2006)

Abstract - Classical swine fever virus replicon particles
(CSF-VRP) deficient for E
were evaluated as a non-transmissible marker
vaccine. A cDNA clone of CSFV strain Alfort/187 was used to obtain a
replication-competent mutant genome (replicon) lacking the sequence encoding
the 227 amino acids of the glycoprotein E
(A187delE
). For packaging of
A187delE
into virus particles, porcine kidney cell lines constitutively
expressing E
of CSFV were established. The rescued VRP were infectious in
cell culture but did not yield infectious progeny virus. Single intradermal
vaccination of two pigs with 107 TCID50 of VRP A187delE
elicited
neutralizing antibodies, anti-E2 antibodies, and cellular immune responses
determined by an increase of IFN- producing cells. No
anti-E
antibodies were detected in the vaccinees confirming that this
vaccine represents a negative marker vaccine allowing differentiation
between infected and vaccinated animals. The two pigs were protected against
lethal challenge with the highly virulent CSFV strain Eystrup. In contrast,
oral immunization resulted in only partial protection, and neither
CSFV-specific antibodies nor stimulated T-cells were found before challenge.
These data represent a good basis for more extended vaccination/challenge
trials including larger numbers of animals as well as more thorough analysis
of virus shedding using sentinel animals to monitor horizontal spread of the
challenge virus.